4.4-stable review patch. If anyone has any objections, please let me know.
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From: Toshi Kani toshi.kani@hpe.com
commit f967db0b9ed44ec3057a28f3b28efc51df51b835 upstream.
ioremap() supports pmd mappings on x86-PAE. However, kernel's pmd tables are not shared among processes on x86-PAE. Therefore, any update to sync'd pmd entries need re-syncing. Freeing a pte page also leads to a vmalloc fault and hits the BUG_ON in vmalloc_sync_one().
Disable free page handling on x86-PAE. pud_free_pmd_page() and pmd_free_pte_page() simply return 0 if a given pud/pmd entry is present. This assures that ioremap() does not update sync'd pmd entries at the cost of falling back to pte mappings.
Fixes: 28ee90fe6048 ("x86/mm: implement free pmd/pte page interfaces") Reported-by: Joerg Roedel joro@8bytes.org Signed-off-by: Toshi Kani toshi.kani@hpe.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: mhocko@suse.com Cc: akpm@linux-foundation.org Cc: hpa@zytor.com Cc: cpandya@codeaurora.org Cc: linux-mm@kvack.org Cc: linux-arm-kernel@lists.infradead.org Cc: stable@vger.kernel.org Cc: Andrew Morton akpm@linux-foundation.org Cc: Michal Hocko mhocko@suse.com Cc: "H. Peter Anvin" hpa@zytor.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180627141348.21777-2-toshi.kani@hpe.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/mm/pgtable.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
--- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -676,6 +676,7 @@ int pmd_clear_huge(pmd_t *pmd) return 0; }
+#ifdef CONFIG_X86_64 /** * pud_free_pmd_page - Clear pud entry and free pmd page. * @pud: Pointer to a PUD. @@ -723,4 +724,22 @@ int pmd_free_pte_page(pmd_t *pmd)
return 1; } + +#else /* !CONFIG_X86_64 */ + +int pud_free_pmd_page(pud_t *pud) +{ + return pud_none(*pud); +} + +/* + * Disable free page handling on x86-PAE. This assures that ioremap() + * does not update sync'd pmd entries. See vmalloc_sync_one(). + */ +int pmd_free_pte_page(pmd_t *pmd) +{ + return pmd_none(*pmd); +} + +#endif /* CONFIG_X86_64 */ #endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */